China is facing a double challenge of both HIV/AIDS and drug abuse epidemics. Injection drug users (IDUS) are the driving force of HIV/AIDS epidemics and female injection drug users appear to be at higher risk for HIV infection. In recent years, scientific knowledge about gender-related differences in drug use and HIV/AIDS has increased, but in China, such information is absent although drug use among women and HIV infection is increasing rapidly. The available studies done in China on HIV/AIDS and IDUs are cross-sectional investigations in high HIV prevalence rural areas;few studies have been done in urban areas. In order to fill these gaps on information, we propose a longitudinal study to understand the gender difference of HIV risk behaviors and drug use among IDUs in Shanghai, China, an area with a low prevalence of HIV infection. This prospective epidemiological research will focus specifically on exploring gender effects on changes of HIV risk behaviors and the prevalence and incidence of HIV, HCV and HBV infections and factors lead to HIV incidence during a 24 month follow-up period by conducting both qualitative and quantitative studies. This study also will allow us to determine whether the low HIV prevalence will be maintained during a 24 month follow-up period and will explore factors that contribute to the low HIV prevalence rate in Shanghai. This kind of research will be very important to fill the research gap in China and the insights from it will provide very important information for effective HIV/AIDS surveillance and intervention strategies. Based on this study, effective HIV/AIDS prevention/intervention and drug treatment programs in China may be planned and implemented to decrease the HIV epidemic among IDUs and prevent the potential for the transmission of HIV infection from high risk groups such as IDUs to other populations. This proposal is the result of collaborative efforts among a NIDA-supported foreign research trainee upon returning to her home institution at Shanghai Mental Health Center and her mentors at University of Miami, and it will lead to further expansion of collaboration on HIV/AIDS and drug abuse research between Shanghai and Miami.